Art of aerating viscous liquids



June 3, 1941. H. w. GREENUP ET AL ART OF AERATING VISCOUS LIQUL EDS Filed May 8, 1957 7 Sheets-Sheet l INVENTIORS HAROLD W. GREENUP AND NORRIS Jofl/v o/v BY W ATTORNEY June 3, 1941. H w GREENUP ETAL 2,244,616

ART OF AERATING VISCOUS LIQUIDS Filed May 8, 1957 7 sheets-sheet 2 HAROLD 14/. GREENUP AND NORRIS fo/v/vsro/v IAT- RNEY J1me 1941- H. w. GREENUP ETAL 2,244,616

ART OF AERATING' VISCOUS LIQUIDS Filed May 8, 1937 7 Sheets-Sheet 3 AND NOR/W5 .ToH/vs To/v BY f fi/ I ATTO EY June 3, 1941. H. w. GREENUP ET AL ART OF AERATING VISCOUS LIQUIDS Filed May 8, 1937 '7 Sheets-Sheet 4 INVENTORS HAROLD W GREE/vz/P 5 N R W m fi om J 1941. H. w. GREENUP ETAL 2,244,615

ART OF AERATING VISCOUS LIQUIDS Filed May 8, 1957 7 Sheets-Sheet 5 II I "I I I i 3U l 11 nvvz/vraxs HAROLD V14 GREENz/P AND ATTOR June 3, 1941. H. w. GREENUP ET AL ART OF AERATING VISCOUS LIQUIDS Filed May 8, 1937 7 She'ets-Sheet 6 INVENTORS HAROLD PM GREENUP 2 AND Nam/s ioH/vsrm/ Q/fix Q? ATTORNEY H. W. GREENUP ETAL ART OF AERATING VISCOUS LIQUIDS June 3, 1941.

Filed May 8, 1937 7 Sheets-Sheet 7 INVENTOR: HAROLD m GREENUP AND N0 R s JOHN B) j OR Y ATT v Figure 9;

Patented June 3, 1941- ART OF AERATING VISCOUS LIQUIDS Harold W. Greenup, Akron, and Norris Johnston,

Cuyahoga Falls, Ohio, assignors to The Firestone Tire & Rubber Company, Akron, Ohio, a

corporation of Ohio Application May 8, 1937, Serial No. 141,580

3 Claims. (Cl. 260-723) This invention relates to the art of aerating viscous liquids, and more especially it relates v to improved procedure for frothing aqueous dispersions of rubber.

The invention is of especial utility in the manufacture of vulcanized cellular or sponge rubber structures wherein the size of the cells is an important consideration, said cells being the result of the air bubbles with which the unvulcanized rubber dispersion is impregnated. By means of the present invention the size of the air bubbles may be controlled.

The chief object of the invention is to provide an improved method for frothing rubber latex. More specifically, the invention aims to produce a latex froth wherein the air bubbles are of small unit size: to provide a system for the continuous production of latex froth; to obviate coagulation of the latex resulting from violent impact there of with the aerating apparatus; and to provide against splatter of the latex so that aeration thereof may be effected in open vessels, and mechanical difliculties arising from latex in machinery bearings will be avoided. Other objects will be manifest as the specification proceeds.

Of the accompanying drawings:

Figure l is a plan view of apparatus adapted to carry out the invention, in its preferred form;

Figure 2 is a side elevation thereof;

Figure 3 is a section on the line 3-3 of Figure 1 and Figure 4;

Figure 4 is a section on the line 4-4 of Figure 2 and Figure 3;

Figure 5 is a section, on a larger scale, on the line 5-6 of Figure 2;

Figure 6 is a section, on a larger scale, on the line 63 of Figure 2;

Figure 7 is a section, on a larger scale, on the line l-'| of Figure 2;

Figure 8 is a side elevation of another embodiment of the invention; v

Figure 9 is a vertical section .through a portion of the structure shown in Figure 8;

Figure 10 is a section on the line Ill-Ill of Figure 11 is a plan view of still another embodiment of the invention; and

Figure 12 is a section on the line I2-I2 of Figure 11.

Briefly stated, the improved aerating method consists in forming a continuous stream of compounded rubber latex, eflecting a gravity induced flow thereof by directing it in a course extending from a higher to a lower level, and subjecting the latex to a beating or whipping action at successive local regions longitudinally of said course.

The preferred apparatus for the practice of the aforesaid method is shown in Figures 1 to 7 in-' elusive, and a plurality of apparatus units may be arranged in side by side relation to conserve floor space, and to permit .the use of structures common to two or more units, as is clearly shown in Figure 1. The apparatus comprises an open framework I5 that carries a tank I6 at one end thereof and at a low elevation, said tank extending entirely across the framework and con stituting a receptacle for receiving liquid latex that overflows from a plurality of receptacles positioned at a higher elevation, as presently will be explained. The tank I6 is provided with a closable drain pipe I! in its bottom for removing liquid therefrom. Mounted upon the top of .the

framework I5, at the same end thereof as the tank I6, are two receptacles or tanks I8, l8 for receiving a. supply of compounded liquid latexthat subsequently is to be aerated. In each receptacle I8 is an agitator I9 driven by a motor 20 atop the receptacle, said agitator keeping the latex in the receptacle in motion so as to maintain the latex at uniform consistency. The two receptacles I8 supply latex to four units of aerating apparatus, and positioned between the latter and .said receptacles are devices for assuring uniform flow of latex notwithstanding variation in the head of liquid in the receptacles.

Said devices comprise small distributor receptacles 2i, 2!, each of which is associated with a receptacle I8 and receives latex therefrom by gravity flow through a suitably valved pipe 22. The bottom of each distributor receptacle is provided with two delivery pipes or nozzles 23, 23

that are spaced apart so as to be positioned over the receiving ends of respective aerating units. The lower end of each pipe 23 is provided with a removable apertured cap 24 that may be replaced by other caps having apertures of different sizes whereby the size of the stream of latex. flowing to the aerating units is controlled. Below the level of the inlet pipe 22, each distributor receptacle is provided with an overflow port 25 conaerating units is achieved.

The four aerating units shown are arranged in pairs in that they deliver the frothed latex into but two delivery troughs at their deliveryends, In other respects the units are separate from each other, and are identical in structure so that a description of one will suflice for all. As shown in Figures 2 and 3, the framework |5 includes a plurality of parallel frame members |5a that extend substantially from end to end of the framework, and slope somewhat downwardly from the receiving end of the apparatus toward the delivery end thereof. Suspended between a pair of adjacent frame members |5a is a troughlike structure consisting of a series of contiguous, open compartments 33, 33 of which adjacent compartments are separated by respective walls or partitions 3|, 3|. The bottom of each compartment is horizontally disposed so that the structure presents a stepped appearance, and

said bottoms are transversely rounded or concave, and provided with respective suitably capped drainage orifices 32. As is most clearly shown in Figures 3 and 4, the partitions 3| are deeply notched, as at 3|a, to permit liquid in each compartment 33 to overflow into the adjacent lower compartment. The notches 3|a are of different depths, varying from a relatively deep notch in the partition between the two uppermost compartments to a relatively shallow notch on the delivery side of the lowermost compartment. The arrangement is such that the successive compartments 33, from the receiving toward the delivery end of the apparatus, are of progressively increased capacity. Since all of the compartments are of the same area. this means that the depth of the liquid in the compartments at the lower end of the series is greater than the depth of the liquid in the upper compartments. The uppermost compartment 33 is below one of the delivery pipes 23 of a distributor receptacle 2|.

Positioned within each compartment 33 of the series is a rotary beater or whip 35 which may be of the type and size commonly in household use. As is most clearly shown in- Figure 3, such beaters comprise two rotary beater elements that are suitably geared together within a housing 36.- The latter is adjustably mounted upon an upright stem or stud 31 that is carried by a bracket arm 38, said arm being secured to a frame member |5a at one side of the compartment. For driving the beater 35, the shaft or stem of one of the rotatable elements thereof is provided with a grooved pulley 39 about which is trained a driving belt 43, the latter also being trained about a grooved pulley 4| that is mounted upon a drive shaft 42. The drive shaft 42 is co-extensive with the. series of compartments 33, being journaled in a plurality of bearing brackets 43, 43 that are mounted upon a frame element l5a, on the opposite side of the compartment from the frame element that carries bracket arms 38'. At its upper. end the drive shaft 42 is coupled to the shaft of an electric motor 44 that is mounted upon the framework I5 below the receptacles, l8. The arrangement is such that one motor 44 drives all of the beaters 35 of one aerating unit, which beaters whip the liquid latex into a froth.

At the delivery end of the aerating unit, the lowermost compartment 33 thereof discharges into an elongate spillway or trough 41, said trough extending transversely of the apparatus so as to function as a spillway for two of the aerating units. At one of its ends the trough 41 is provided with discharge spout 48 through which the aerated fluid will flow by gravity, said spout being pivotally mounted so as to be anguaerated liquid from the delivery spouts 48. As

shownin Figure 5, each receptacle 53 is a cylindrical structure that has a closable, axial drainage port 5| in its bottom. The re eptacle .53 is rotated upon its axis, and means is provided foi stirring the frothed latex that flows thereinto, to maintain the latter at uniform consistency and to assure proper admixing therewith of other constituents, such as a coagulating medium, that is introduced into a batch of froth immediately before the froth is poured into a mold. The swingable feature of each spout 48 makes it possible for the spout to discharge into one receptacle 53 while the adjacent receptacle is removed from the apparatus for emptying and cleaning.

For effecting rotation of the receptacles 53, each of them is mounted upon a turntable 52 that is supported upon a bearing structure 53 carried by a shelf 54 on the framework l5. The turntable 52 is peripherally grooved to receive a driving belt 55 that also passes around a driving pulley 58 that is mounted upon a shaft 51, the latter also carrying a sprocket 58. The latter is engaged by a sprocket chain 53 that is driven by a sprocket 83 of a reduction gear device 6|, and the reduction gear device is driven by a motor 82 to which it is coupled, said motor being mounted upon framework I5, near the bottom thereof. The turntable 52 is formed with an axial opening to receive a pilot structure 63 on the bottom of receptacle 53 for centering the receptacle on the turntable. There is but one motor 52, reduction gear device 6| and shaft 51, the latter carrying four pulleys 55 by means of which all four receptacles 53 are rotated.

For stirring the contents of each receptacle 53, an agitator is provided, which agitator has an operative position within the receptacle and an inoperative position above the same. The agitator 85 is somewhat similar to the beaters 35, but is larger and longer. It comprises two rotary elements that are geared together at their upper ends, the gears being enclosed in a housing structure 66. The latter comprises a top plate that projects laterally of the housing, and is formed with a pair of spaced apart apertures in which are receivable a pair of studs 61. 31 that project upwardly from a cross-member 68 carried by the framework l5. The arrangement is such that the agitator will be supported by cross-member 58 when it is in operative position, the studs 81 preventing angular movement of the agitator from torque reaction during the operation thereof.

The agitator 55 is driven by means of a vertical drive shaft 13 connected at its lower end to one of the rotatable elements of the agitator. The shaft 13 extends upwardly through a gear box 1| mounted upon a shelf 12 upon the top of the framework I5. Keyed upon shaft 13, within said gear box, is a bevel gear 13, said shaft being formed with an elongate keyway 14 so that it may be moved axially, relatively of said gear. Meshed with gear 13 is a bevel gear 15 that is directly connected to the shaft of a motor 16 so as to be driven thereby, said motor being mounted upon the shelf 12 exteriorly of the gear box 1|. The upper end of the shaft 13 is provided with a loop 11 whereby it may be manually grasped for lifting the shaft and thereby raising the agitator out of the receptacle W, as indicated in broken lines in Figure 5. For retaining the agitator in raised, inoperative position a pair of pendulous hooks l8, 18 are mounted upon the" under side of shelf 12, said hooks being adapted I uous production of aerated latex. The comto engage the under side of housing structure 86.- I

in the elevated position of the latter, as shown in Figure 5. I

Because the notches 8la'of the partitions 3| are of greater depth between the compartments 30 at the upper or receiving end of the series, it follows that the depth of the liquid in the respective compartments will be progressively greater toward the lower or delivery end of the series. And this differential in depth will be accentuated by reason of the frothing of the liquid, whichincreases the viscosity of the liquid and causes it to flow from one compartment to the next in a progressively thicker stream. All of the beaters 35 are positioned in the respective compartments 38 at the same distance from the bottoms thereof, with the result that they are thereby immersed to different depths in the liquid therein. At the upper end of the series of compartments the beater is only about half submerged. In the lowermost compartment the.

beater is disposed well below the level of the froth.

The action of the beaters in the liquid latex is to whip the latter, and set up a circulation of the liquid which causes it to flow outwar'dly away from the beater near the bottom ofthe container, thence upwardly along the sides of the container, and then inwardly toward the beater at the top of the body of liquid. Because it is desirable that all the liquid in each container be set in circulation, the size of the container bears a definite relation to the size of the beater. Best results are obtained if the greatest widthof the container is not more than four times'the greatest width of the beater. The speed at which the beaters are driven also is important, since it must be great enough to produce a substantial vortex. Experience has shown that a speed of. 1,100 R. P. M. gives satisfactory results. cause of the latter, and because the beaters at the receiving end of the series of compartments are not completely submerged in the latex, the result of the beating is to impregnate the latex with a multiplicity of relatively large air bubbles, thus 7 forming a froth. As the latter cascades to the other, lower compartments 30, it is subjected to successive whipping actions by the other beaters. Because the latter are completely submerged in the froth, their action does not draw more air into the froth, but breaks up and divides the bubbles already therein so that the froth that flows into trough 41 is extremely light and viscous, and of much greater volume than the stream flowing from nozzle 23.

Splattering of the latex during the frothing thereof is undesirable for the reason that it causes coagulation of the particles that are subiected to violent impact. The viscosity of the latex is a factor that affects splatter, so also is the peripheral velocity of the beater elements. Since the beaters are required to rotate at sufficient speed to cause the latex to assume a vortex, it is necessary that the size of the beaters be as small as is practicable. It is for this reason that beaters of the size usually found in domestic service are preferred.

The apparatus described achieves the continpounded liquid latex flows in a uniform stream into the uppermost of the compartments 80, where it .is whipped into a froth containing relatively large air bubbles, and overflows therefrom into a succession of other compartments where the whipping is repeated to reduce the size of the said air-bubbles. From the lowermost compartment 30 the froth flows through spout 48 to one of the receptacles 50 where it is continuously stirred until a sufficient amount accumulates to constitute a batch. Thereupon other ingredients,

including a coagulant, are stirred into the batch, after which the drive of motor I8 is stopped, the agitator 65 is elevated to inoperative position, and the receptacle 50 removed from the apparatus and its contents disposed of. Before the receptacle 50 is removed as described. the spout 48 is swung angularly so as to discharge into an adjacent receptacle I50.

Aside from the advantages accruing from continuous production, the invention provides for the mechanical frothing of latex, it provides a superior product due to the absence of frothing agents, and it achieves the other advantages set out in the foregoing statement of objects.

The embodiment of the invention shown in Figures 8 to 10 inclusive consists of a single apparatus unit that is essentially similar to a unit of the apparatus previously described, so that a detail description of the modified structure will not be required. The primary difference between the two embodiments is the feature of an individual drive for each of the beater devices. As is shown most clearly in Figure 10, each beater is driven by an electric motor that is mounted within a housing 8i, said motor being connected with a source of power through conductor cord 82. The housing 8i is mounted upon the overhanging portion of an inverted L-shaped bracket arm 83 that is bolted or otherwise secured to an angle member 84 that constitutes a part of the framework of the apparatus. Preferably the attaching bolts extend through a slot 85 extending longitudinally of the bracket arm, whereby vertical adjustment of the latter is effected. The arrangement permits the beater to be positioned at the optimum distance from the bottom ofthe latex compartment. Fig. 9 most clearly shows the relation of the beaters to the height of the partitions between the adjacent compartments.

The beaters 80, like all household beaters, are

equipped with means for varying their speed, the usual arrangement providing three different speeds. This makes it possible to drive the heaters at optimum speed, or at differential speeds if better results may be obtained thereby. Thus the modified embodiment of the invention possesses greater flexibility than that previously described.

The modified embodiment of the invention shown in Figs. 11 and 12 differs essentially from those previously described in that it does not.

produce a continuous supply of froth. It comprises a table 88 of which the middle portion consists of a circular turntable 88 that rests upon pivoted, the arrangement being such that the heaters may be positioned within the trough 82, as shown, or tilted backward away from the trough to permit the latter to be lifted OK the turntable. The turntable I! and trough 82 are rotated about their common axis by means of a drive belt 91 that is trained about the outer periphery of the trough, and about a drive pulley 08 that is carried upon the shaft of a motor 99, the latter being mounted, upon a vertical axis, upon the side of table 88. V

In the operation of this embodiment of the invention, a quantity of compounded rubber latex, suflicient almost to cover the beater elements as shown, is placed in thetrough 92. The latter is then rotated and the several heaters put into operation, with the result that the liquid in the trough is carried past the heaters in continuous succession, said heaters w ipping the liquid into a froth. When the froth attains the desired consistency, the operation is concluded, the heaters are tilted, and the trough removed from the turntable and emptied.

It will be seen that the apparatus depicted in Figures 11 and 12 is not continuous in operation, that it prepares but one hatch at a time, and that the size of the batch is definitely limited. The quality of the froth produced, however, is satisfactory, and other objects of the invention are achieved.

Other modification may be resorted to without departing from the spirit of the invention, or the scope of the invention as defined by the appended claims.

What is claimed is:

1. That method of aerating latex which comprises whipping the latex with a heater that is only partially submerged therein to form a foam of latex containing relatively large air bubbles, transferring the foam, and whipping the foam with a plurality of separate heaters that are progressively submerged in the foam further than whipping the foam with a heater substantially totally submerged in the foam, transferring the foam, and whipping the foam to produce. small bubbles in the foam by a beater which is totally submerged in the foam.

3. That method of aerating latex which comprises initially whipping latex with a heater that is about one-half way submerged in the latex to form a foamcontaining relatively large air bubbles, flowing the foam to a second position. whipping the foam with a beater that is over half-way submerged in the foam to reduce the size of bubbles therein, and repeating the steps of flowing the foam to a new position and whipping it with a heater at that position which is progressively further submerged in the foam at each position until the foam is whipped by a beater which is totally submerged and the foam is composed of small bubbles.

' HAROLD W. GREENUP.

NORRIS JOHNSTON. 

